Transmitter and transmission method

ABSTRACT

The present invention provides a transmitter which can suitably perform a transmission power control in a PT-RS port. In this transmitter ( 100 ), a control unit ( 101 ) determines a transmission power for transmitting a reference signal (PT-RS) for phase tracking and a data signal within a range in which the maximum transmission power for each antenna port is not exceeded. In addition, a transmission unit ( 105 ) transmits the reference signal for phase tracking and the data signal at the transmission power determined by the control unit ( 101 ).

TECHNICAL FIELD

The present disclosure relates to a transmitter and a transmissionmethod.

BACKGROUND ART

Studies have been carried out on communication systems so called the5^(th) Generation mobile communication systems (5G). In 5G, studies havebeen carried out on flexibly providing functions for each of use caseswhich require an increase in communication traffic, an increase in thenumber of terminals to be connected, high reliability, and low latency.Typical use cases include the following three: enhanced Mobile Broadband(eMBB); massive Machine Type Communications (mMTC); and Ultra Reliableand Low Latency Communications (URLLC). In the 3 rd GenerationPartnership Project (3GPP), which is an international standardizationorganization, further advancement of communication systems has beenunder study in both aspects of advancement of the LTE systems, and NewRadio Access Technology (New RAT) (e.g., see Non-Patent Literature(hereinafter, referred to as “NPL”) 1).

CITATION LIST Non-Patent Literature

-   NPL 1

RP-161596, “Revision of SI: Study on New Radio Access Technology,” NTTDOCOMO, September 2016

-   NPL 2

R1-1612335, “On phase noise effects,” Ericsson, November 2016

-   NPL 3

3GPP TS 38.214 V15.0.0, “NR Physical layer procedure for data (Release15)” (2017-12)

-   NPL 4

R1-1611665, “Multi-panel based UL MIMO transmission,” Huawei, HiSilicon,November 2016

-   NPL 5

3GPP TS 38.211 V15.0.0, “NR Physical channels and modulation (Release15)” (2017-12)

SUMMARY

In New RAT, for example, signals of a frequency equal to or greater than6 GHz is used as a carrier wave. In particular, when a high frequencyband and high modulation order are used, error rate characteristics aredegraded due to Common Phase Error (CPE) or Inter-Carrier Interference(ICI), which occurs due to a phase noise of a local oscillator (e.g.,see NPL 2). In this respect, in New RAT, performing of CPE correction orICI correction (hereinafter, may be referred to as “CPE/ICI correction”)using Phase Tracking Reference Signal (PT-RS) in addition to channelequalization by receivers have been under study.

Further studies regarding transmission power control in antenna portsthrough which a PT-RS is transmitted (hereinafter, may be referred to as“PT-RS port”) are necessary, however.

One non-limiting and exemplary embodiment of the present disclosurefacilitates providing a transmitter and a transmission method eachcapable of appropriately performing transmission power control in aPT-RS port.

A transmitter according to one aspect of the present disclosureincludes: control circuitry, which, in operation, determines atransmission power for a phase tracking reference signal (PT-RS) and adata signal within a range not exceeding a maximum transmission powerfor each antenna port; and transmission circuitry, which, in operation,transmits the PT-RS and the data signal with the determined transmissionpower.

A transmission method according to one aspect of the present disclosureincludes: determining a transmission power for a phase trackingreference signal (PT-RS) and a data signal within a range not exceedinga maximum transmission power for each antenna port; and transmitting thePT-RS and the data signal with the determined transmission power.

It should be noted that general or specific embodiments may beimplemented as a system, an apparatus, a method, an integrated circuit,a computer program or a recording medium, or any selective combinationof the system, the apparatus, the method, the integrated circuit, thecomputer program, and the recording medium.

According to one exemplary embodiment of this disclosure, transmissionpower control in PT-RS ports can be appropriately performed.

Additional benefits and advantages of the disclosed exemplaryembodiments will become apparent from the specification and drawings.The benefits and/or advantages may be individually obtained by variousembodiments and features of the specification and drawings, which neednot all be provided in order to obtain one or more of such benefitsand/or advantages.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a mapping example of DMRS and PT-RS inMIMO;

FIG. 2 is a diagram illustrating an exemplary power boosting;

FIG. 3 is a diagram illustrating an exemplary non-coherent transmissionand coherent transmission;

FIG. 4 is a diagram illustrating a PT-RS transmission example innon-coherent transmission;

FIG. 5 is a block diagram illustrating a configuration of a part of atransmitter according to Embodiment 1;

FIG. 6 is a block diagram illustrating a configuration of thetransmitter according to Embodiment 1;

FIG. 7 is a block diagram illustrating a configuration of a receiveraccording to Embodiment 1;

FIG. 8 is a flowchart illustrating an operation of the transmitteraccording to Embodiment 1;

FIG. 9 is a diagram illustrating an exemplary transmission poweradjustment according to Operation Example 1 of Embodiment 1;

FIG. 10 is a diagram illustrating an exemplary transmission poweradjustment according to Operation Example 2 of Embodiment 1;

FIG. 11 is a diagram illustrating an exemplary transmission poweradjustment according to Operation Example 3 of Embodiment 1;

FIG. 12 is a diagram illustrating an exemplary transmission poweradjustment according to Operation Example 4 of Embodiment 1;

FIG. 13 is a diagram illustrating an exemplary transmission poweradjustment according to Operation Example 5 of Embodiment 1;

FIG. 14 is a block diagram illustrating a configuration example of atransmitter according to Embodiment 2;

FIG. 15 is a block diagram illustrating a configuration example of areceiver according to Embodiment 2;

FIG. 16 is a block diagram illustrating a configuration example of atransmitter according to Embodiment 3; and

FIG. 17 is a block diagram illustrating a configuration example of areceiver according to Embodiment 3.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a detailed description will be given of embodiments of thepresent disclosure with reference to the accompanying drawings.

[Power Boosting]

In a case where the number of antenna ports (PT-RS ports) fortransmitting PT-RS and the number of antenna ports (DMRS ports) fortransmitting data and DMRS are different from each other, thetransmission power per Resource Element (hereinafter, ma be referred toas “RE” and/or resource elements may be collectively referred to as“RE”) of PT-RS in one antenna port may be configured to be largecompared with the transmission power per RE of data in one antenna portto be transmitted and received between the same base station and mobilestation. This transmission power control for PT-RS may be referred to as“power boosting.” Power boosting of PT-RS improves the PT-RS receptionaccuracy and CPE/ICI estimation accuracy, and thus, improvement in thetransmission speed/transmission efficiency can be expected.

It is also assumed that coherent transmission (full-coherenttransmission), non-coherent transmission (non-coherent transmission),and partial coherent transmission (partial-coherent transmission) aresupported in codebook based uplink transmission of NR. Among thesetransmissions, there is an opinion that power boosting of PT-RS isdifficult in non-coherent transmissions and partial coherenttransmissions because the upper limit of transmission power (maximumtransmission power) is provided for each antenna port. However, for moreaccurate CPE/ICI estimation, PT-RS should be subjected to power boostingas much as possible in all transmission schemes. Therefore, a method forapplying power boosting to PT-RS (PT-RS power boosting) in non-coherenttransmission or partial coherent transmission needs to be discussed.

[PT-RS]

The higher the frequency band to which the signal is assigned or thehigher the modulation order to be used for the signal, the greater theeffect of CPE/ICI for the error rate characteristics is. Therefore, asdescribed above, in a case where a high-frequency band and/or highmodulation order is used, performing of CPE/ICI correction using PT-RSin addition to channel equalization in receivers has been discussed.

PT-RS is mapped with high density on the time domain compared with areference signal for channel estimation (for demodulation) (DemodulationReference Signal (DMRS)) in order to track CPE/ICI that fluctuatesrandomly in time. Specifically, it is assumed that PT-RS is mapped witha density of each symbol, one symbol of two adjacent symbols or onesymbol of four adjacent symbols, for example. Further, because of thecharacteristics that the variation between CPE/ICI subcarriers is small,PT-RS is mapped with a relatively low density in frequency domain.Specifically, it is assumed that PT-RS is mapped in a density, such asone for each Resource Block (RB) (e.g., one subcarrier), one for everyadjacent two RBs, or one for every adjacent four RBs.

According to the agreements regarding PT-RS in 3GPP RAN1 #88, PT-RS isused between a base station (BS, eNB, gNB) and a mobile station(terminal, UE) as indicated by higher layer signaling (e.g., RRC (RadioResource Control) signaling) from the base station.

It is also assumed that assignment densities of PT-RS in the time domainand frequency domain flexibly change depending on the modulation orderor bandwidth and/or the like used between the base station and themobile station.

In addition, a method for determining the assignment density of PT-RS(hereinafter, may be referred to as “PT-RS assignment density”) bymobile stations has been discussed.

As one method, there is a method in which the PT-RS assignment densityis indicated from the base station by a PT-RS dedicated control signal(e.g., Downlink Control Information (DCI)) or an RRC signal) (explicitindication). As another method, there is a method in which acorrespondence relationship between the PT-RS assignment density andanother parameter (e.g., such as a modulation order or bandwidth) ispreviously determined, and a mobile station determines the PT-RSassignment density by checking the correspondence relationship with theother parameter indicated by DCI at the time of communication (implicitindication). Note that there is a possibility that a method other thanthese methods may be used.

Meanwhile, DMRS used for channel estimation is mapped with a highdensity in frequency domain and a low density in time domain comparedwith PT-RS, because the change in channel characteristics in infrequency domain is large and the change in time domain is not as largeas phase noise. Furthermore, in order to set the timing of datademodulation earlier, the introduction of a front-loaded DMRS which ismapped in a front position of a slot is assumed in New RAT.

Further, mapping of PT-RS to the same antenna port as a certain DMRS(this port may be referred to as “PT-RS port”) and application of thesame precoding as a DMRS port to PT-RS have been discussed. For thisreason, there is a possibility that PT-RS may be used in the receiverfor channel estimation as with DMRS.

Further, there is a possibility that PT-RS is defined as a part of DMRS.In this case, DMRS used as PT-RS is mapped with a high density comparedwith other DMRSs in time domain and is mapped with a low densitycompared with other DMRSs in frequency domain. Further, the referencesignal used to correct CPE/ICI generated due to phase noise may also bereferred to as a term other than “PT-RS.”

It is also assumed that Multiple Input Multiple Output (MIMO) is used inNew RAT. That is, the base station and one or more mobile stationswithin a cell formed by the base station are capable of performingtransmission and reception, using a plurality of antenna portscorresponding to different precoding pieces using the same time andfrequency resources.

In the base station and the mobile station, there are limits on theirrespective maximum transmission powers. For this reason, it is assumedthat the operation is performed such that the sum of the transmissionpowers of the plurality of antenna ports used for data transmission doesnot exceed the maximum value of the transmission power. Basically, it isassumed that the transmission powers for data of the antenna ports areequal to each other. Therefore, for example, in case of transmission ofdata or a reference signal, using one antenna port and in case oftransmission of data or a reference signal, using n antenna ports, thetransmission power per antenna port is considered to be n times largerin the former than that in the latter.

PT-RS is transmitted and received between the base station and each ofthe mobile stations in a cell formed by the base station. Herein, in agroup of antenna ports (may be referred to as a DMRS port group) sharinga local oscillator of a transmitter (base station in downlink and mobilestations in uplink), the values of CPE/ICI are likely to be the same.For this reason, it is assumed that PT-RS is transmitted from any oneantenna port of this group.

Furthermore, it is considered that PT-RS transmitted and received withrespect to one mobile station is subjected to time/frequency/spatiallyorthogonal multiplexing with respect to data. Therefore, in a case wherePT-RS is transmitted in a certain antenna port (a certain RE), nothingis transmitted on the RE in other antenna ports used by the mobilestation. In other words, in a certain RE, power is used for PT-RS in oneantenna port, and no power is used (nothing is transmitted) at all inthe other antenna ports.

In New RAT, the following transmission power control, i.e., “PT-RS powerboosting” has been under discussion. In this transmission power control,the transmission power per RE of one antenna port for PT-RS is madelarger than the transmission power per RE of one antenna port for data,using the power of resources not used by the other antenna ports, by theamount of power of the not used resources.

As an example, FIG. 1 illustrates a mapping example of DMRS, PT-RS anddata in MIMO. In RE (symbol×subcarrier) at the lowermost subcarrier ofFIG. 1, PT-RS is transmitted in antenna port 1000. At this time, in thesame RE group (i.e., the lowest subcarrier) as the RE group on whichPT-RS is transmitted in antenna port 1000, nothing is transmitted inantenna port 1001 (blank).

FIG. 2 illustrates an example of transmission power allocation in RE ofeach of antenna ports 1000 and 1001 before and after PT-RS powerboosting is performed. In the example illustrated in FIG. 2, antennaport 1000 adds (power boosting) the power of RE not used in antenna port1001 to PT-RS and transmits the PT-RS. Therefore, after PT-RS powerboosting, as illustrated in FIG. 2, not only the RE on which PT-RS istransmitted but also the transmission power of the entire antenna port1000 becomes larger than the transmission power of antenna port 1001.

According to the description of uplink PT-RS power boosting in NPL 3,herein, when PT-RS is transmitted in one antenna port (one PT-RS port)in uplink, the ratio representing “how many times the power of data isthe power of PT-RS” for every RE in PT-RS port is, ρ_(PTRS,i), and isobtained by the following equation.

-   [Equation 1]

ρ_(PTRS,i)=−10 log₁₀(n _(layer) ^(PUSCH))   (1)

In Equation 1, n_(layer) ^(PUSCH) represents the number of layers oftransmission data configured in the base station (i.e., the receiver).

[Precoding of Transmitter]

For uplink transmission of New RAT, two transmission methods (e.g.,codebook based transmission (codebook based UL transmission) andnon-codebook based transmission (non-codebook based UL transmission) areassumed (e.g., see NPL 3). In codebook based transmission, the number ofavailable precoding matrices differs depending on the type of coherenttransmission that can be supported by the mobile station. It is assumedthat the types of the capability of the mobile station (UE capability)for coherent transmission are divided into the following three.

fullAndPartialAndNonCoherent

partialAndNonCoherent

Non-Coherent

The first one, which is “fullAndPartialAndNonCoherent,” indicates thepresence of the capability of supporting all types of coherenttransmissions. The second one, which is “partialAndNonCoherent,”indicates the presence of the capability of supporting partial coherenttransmission and non-coherent transmission. The third one, which is“Non-Coherent,” indicates the presence of the capability of supportingonly non-coherent transmission.

“Non-coherent transmission,” herein, is a transmission scheme in whichindependent precoding is applied to different antenna panels in atransmitter in which a plurality of non-uniform antenna panels areimplemented (e.g., see NPL 4). In this case, data on different layers istransmitted from different panels. “Coherent transmission” is atransmission scheme in which data on all layers can be transmitted fromall antenna panels, respectively, in a transmitter in which uniformantenna panels are implemented. Further, “partial coherent transmission”is a transmission method in which data of a part of a layer group istransmitted from a part of an antenna panel group, and data on otherlayers is transmitted from the remaining part of the antenna panelgroup.

Table 1 indicates a precoding matrix assumed to be available when thenumber of layers is two and the number of antenna ports is two (e.g.,see is NPL 5). It is assumed that all matrices in Table 1 are availablefor coherent transmission while only the leftmost matrix in Table 1 isavailable for non-coherent transmission.

TABLE 1 TPMI W index (ordered from left to right in increasing order ofTPMI index) 0-2 $\frac{1}{\sqrt{2}}\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 1 \\1 & {- 1}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 1 \\j & {- j}\end{bmatrix}$

FIG. 3 shows examples of non-coherent transmission and coherenttransmission. As illustrated in FIG. 3, in non-coherent transmission,the data of the respective layers (Layer #1 and # 2) are transmittedfrom independent panels by the precoding matrix.

FIG. 4 illustrates a transmission example of a case where PT-RS istransmitted in non-coherent transmission. As described above, PT-RS maybe transmitted in some of the antenna ports (Port #1 in FIG. 4). Thus,for non-coherent transmission (or partial coherent transmission), thetransmission power of the panel transmitting PT-RS (panel correspondingto Port #1 in FIG. 4) may be greater than the transmission power of theother panel (panel corresponding to Port #2 in FIG. 4). Furthermore,when PT-RS illustrated in FIG. 4 is subjected to power boosting, thetransmission power of the panel may exceed the transmittable power as acapability. As a result, the signal including PT-RS may be distorted orPT-RS may not be transmitted with the intended power, resulting indegradation of CPE/ICI estimation accuracy, which possibly causesdegradation of data transmission efficiency.

Accordingly, in one aspect of the present disclosure, a description willbe given of a method for appropriately performing a transmission powercontrol (including power boosting) for PT-RS in non-coherenttransmission or partial coherent transmission, thereby improving theCPE/ICI estimation accuracy and improving the data transmissionefficiency.

[ Signal Waveforms]

In New RAT, use of a Cyclic Prefix-Orthogonal Frequency DivisionMultiplexing (CP-OFDM) scheme in downlink (direction from a base stationto a mobile station) is assumed. Meanwhile, both the CP-OFDM scheme andDiscrete Fourier Transform-Spread OFDM (DFT-S-OFDM) scheme in uplink(direction from a mobile station to a base station) have been discussed,and it is assumed that the communication schemes are used while they areswitched so as to match the communication environment.

[PHR]

In New RAT, transmission of remaining transmission power information(PHR: Power Headroom Report) as in LTE in uplink transmission isassumed. That is, the mobile station, which is the transmitter, reportsthe value obtained by subtracting the transmission power for the actualdata from the maximum transmission power of the mobile station to thebase station, as PHR. However, the value of PHR is not the remainingtransmission power of each antenna port, and the value of PHR is thevalue as the entire mobile station as a result of aggregating allantenna ports.

Embodiment 1 [Overview of Communication System]

A communication system according to the present embodiment includestransmitter 100 and receiver 200. That is, in uplink, the transmitter isa mobile station and the receiver is a base station. In downlink, thetransmitter is a base station and the receiver is a mobile station.

FIG. 5 is a block diagram illustrating a configuration of a part oftransmitter 100 according to the present embodiment. In transmitter 100illustrated in FIG. 5, controller 101 determines the transmission powerfor phase tracking reference signal (PT-RS) and the data signal within arange not exceeding the maximum transmission power for each antennaport, and transmitter 105 transmits PT-RS and the data signal with thedetermined transmission power.

[Configuration of Transmitter]

FIG. 6 is a block diagram illustrating a configuration of transmitter100 according to the present embodiment. In FIG. 6, transmitter 100includes controller 101, error correction encoder 102, modulator 103,signal assigner 104, transmitter 105, and antenna 106.

Information such as the remaining transmission power of transmitter 100is inputted to controller 101. Controller 101 determines thetransmission power for data or PT-RS and/or the like based on thisinformation and/or the like. Then, controller 101 outputs thetransmission power information indicating the determined transmissionpower to signal assigner 104.

Error correction encoder 102 applies error correction coding on thetransmission data signal to be inputted and outputs the data signalafter the error correction coding to modulator 103.

Modulator 103 applies modulation processing to the signal to be inputtedfrom error correction encoder 102, and outputs the data signal after themodulation to signal assigner 104.

Signal assigner 104 maps DMRS, PT-RS, or the data signal to be inputtedfrom modulator 103 to the time and frequency domain, and outputs signalafter the mapping to transmitter 105. At this time, signal assigner 104configures the transmission power for each signal based on thetransmission power information to be inputted from controller 101.

Transmitter 105 applies radio transmission processing, such as frequencyconversion using a carrier wave, to the signal to be inputted fromsignal assigner 104, and outputs the signal after the radio transmissionprocessing to antenna 106.

Antenna 106 radiates the signal to be inputted from transmitter 105toward receiver 200.

[Configuration of Receiver]

FIG. 7 is a block diagram illustrating a configuration example ofreceiver 200 according to the present embodiment. In FIG. 7, receiver200 includes antenna 201, receiver 202, signal demultiplexer 203,channel estimator 204, CPE/ICI estimator 205, data demodulator 206, anderror correction encoder 207.

Antenna 201 receives the signal transmitted from transmitter 100 (seeFIG. 6) and outputs the received signal to receiver 202.

Receiver 202 applies radio reception processing, such as frequencyconversion to the received signal to be inputted from antenna 201, andoutputs the signal after the radio reception processing to signaldemultiplexer 203.

Signal demultiplexer 203 identifies the positions of the time andfrequency domain to which the data signal, DMRS, and PT-RS in the signalto be inputted from receiver 202 are mapped, and demultiplexes the datasignal, DMRS, and PT-RS. Signal demultiplexer 203 outputs the datasignal in the demultiplexed signal to data demodulator 206, and outputsDMRS to channel estimator 204 and CPE/ICI estimator 205, and outputsPT-RS to channel estimator 204 and CPE/ICI estimator 205.

Channel estimator 204 performs channel estimation, using DMRS to beinputted from signal demultiplexer 203, and outputs a channel estimate(channel information) to data demodulator 206. Note that, channelestimator 204 may perform channel estimation, using PT-RS to be inputtedfrom signal demultiplexer 203. In this case, channel estimator 204 mayperform channel estimation based on PT-RS, using information about theamplitude of PT-RS to be inputted (e.g., the amplitude (power) ratio ofPT-RS to be transmitted from transmitter 100 and the data signal).

CPE/ICI estimator 205 estimates CPE/ICI, using PT-RS and DMRS to beinputted from signal demultiplexer 203, and outputs the CPE/ICI estimateto data demodulator 206.

Data demodulator 206 demodulates the data signal to be inputted fromsignal demultiplexer 203, using a channel estimate to be inputted fromchannel estimator 204 and a CPE/ICI channel estimate to be inputted fromCPE/ICI estimator 205. Data demodulator 206 outputs a demodulationsignal to error correction decoder 207.

Error correction decoder 207 decodes the demodulation signal to beinputted from data demodulator 206 and outputs the resultant receiveddata signal.

[Operations of Transmitter 100 and Receiver 200]

Next, operations of transmitter 100 and receiver 200 will be describedin detail.

FIG. 8 is a flowchart illustrating the processing flow of transmitter100.

Note that transmitter 100 performs, for example, non-coherenttransmission or partial coherent transmission.

First, transmitter 100 (controller 101) configures the transmissionpower for PT-RS and the data signal (DMRS) (ST101). At this time,transmitter 100 may configure the defined transmission power for thedata signal and apply power boosting to PT-RS.

Next, transmitter 100 (controller 101) determines whether or notadjustment of the configured transmission power is required (ST102). Forexample, transmitter 100 determines that adjustment of the transmissionpower is required in a case where the remaining power for transmittingthe signal (PT-RS and data signal) with the transmission powerconfigured in ST101 is not sufficient in the antenna port (PT-RS port)from which the PT-RS is transmitted.

When adjustment of the transmission power is not required (ST102: NO),transmitter 100 proceeds to processing of ST104.

Meanwhile, in a case where adjustment of the transmission power isrequired (ST102: YES), transmitter 100 (controller 101) adjusts thetransmission power such that the transmission power does not exceed themaximum transmission power for each antenna port (i.e., to be equal toor less than the maximum transmission power) (ST103). That is,transmitter 100 reduces the transmission power such that thetransmission power does not exceed the maximum transmission power foreach antenna port in a case where the remaining power for transmittingthe signal with the configured transmission power is not sufficient.

Then, transmitter 100 (transmitter 105) transmits the signal from eachantenna port with the transmission power configured in ST101 or thetransmission power adjusted in ST103 (ST104).

Next, a detailed description will be given of Operation Examples 1 to 5of the transmission power adjustment (ST103 in FIG. 8) by transmitter100 in a case where the remaining transmission power for transmittingthe signal with the configured transmission power is not sufficient.

Note that, hereinafter, a description will be given, as an example, of acase where data (DMRS) and PT-RS are assigned in antenna port 1000, anddata (DMRS) is assigned in antenna port 1001. Transmitter 100 alsoapplies power boosting to PT-RS in non-coherent or partial coherenttransmissions, for example, using a high frequency band and highmodulation order.

In addition, the left sides of FIGS. 9 to 13 illustrate the transmissionpower for each RE to be configured for the data and PT-RS at each ofantenna ports 1000 and 1001 before (before adjustment) reducing thetransmission power, and the right sides of FIGS. 9 to 13 illustrate thetransmission power for each of antenna ports 1000 and 1001 after (afteradjustment) reducing the transmission power, and the transmission powerfor each RE of the data and PT-RS.

<Operation Example 1>

First, transmitter 100, at the i-th PT-RS port, ρ_(PTRS,i) is the ratiorepresenting “how many times the power for data is the power for PT-RS”for every RE, and is determined by the following equation.

-   [Equation 2]

ρ_(PTRS,i)=−10 log₁₀(N _(PTRS) ×n _(DMRS) ^(ptrs,i))   (2)

Herein, NPTRS indicates the number of PT-RS ports (the # of PT-RS portsconfigured with the TX) configured for transmitter 100. Further,n_(DMRS) ^(PTRS) _(,i) indicates the number of DMRS ports belonging tothe DMRS port group associated with the i-th PT-RS port (the # of DMRSports associated with PT-RS port i). For example, in the exampleillustrated in FIG. 9, N_(PTRS)=1, and n_(DMRS) ^(PTRS,i)=2.

Note that, transmitter 100 may calculate the ratio ρ_(PTRS,i) usingEquation 1 instead of Equation 2.

Transmitter 100 then reduces (adjust) the transmission power for thesignal such that the transmission power does not exceed the maximumtransmission power for each antenna port.

FIG. 9 illustrates an example of the transmission power adjustment inOperation Example 1.

As illustrated in FIG. 9, transmitter 100 reduces the transmission powerfor the PT-RS and data signal to be transmitted from all antenna ports1000 and 1001 while maintaining the power ratio ρ_(PTRS,i) between thedata and PT-RS before and after the adjustment. That is, transmitter 100makes a reduction for the PT-RS and data signal of antenna port 1000,which is the PT-RS port, as well as the transmission power of the datasignal of antenna port 1001, which is the other antenna port.

Thus, even after adjustment of the transmission power, the transmissionpower of the data becomes constant (the same) between antenna port, sothat transmitter 100 can fairly transmit the data on all the antennaports.

In addition, since the ratio of the transmission power between the dataand PT-RS does not change before and after adjustment of thetransmission power, the reception processing using the ratio is notaffected.

Further, in a case where receiver 200 receives the informationindicating that “the remaining power for performing transmission withthe configured transmission power in the PT-RS antenna port oftransmitter 100 is not sufficient,” receiver 200 may estimate theamplitude (power) ratio between PT-RS and the data from this informationand perform channel estimation, using the PT-RS based on the estimatedratio.

<Operation Example 2>

FIG. 10 illustrates an example of transmission power adjustment inOperation Example 2.

As illustrated in FIG. 10, transmitter 100 reduces the transmissionpower for the

PT-RS and data signal transmitted in PT-RS port (antenna port 1000)while maintaining the power ratio ρ_(PTRS,i) between the data and PT-RSbefore and after the adjustment. That is, transmitter 100 does notreduce the transmission power in antenna port 1001 which is not a PT-RSport, although transmitter 100 reduces the transmission power in thePT-RS port.

As a result, in the PT-RS port, the ratio of the transmission powerbetween the data and PT-RS does not change before and after adjustmentof the transmission power, so that the reception processing using theratio is not affected.

Further, in the antenna ports other than PT-RS ports, since thetransmission power of the data is not reduced, it is made possible toprevent degradation of the reception accuracy of data in receiver 200.

<Operation Example 3>

FIG. 11 illustrates an example of transmission power adjustment inOperation Example 3.

As illustrated in FIG. 11, transmitter 100 reduces the transmissionpower for the data in the PT-RS port (antenna port 1000) whilemaintaining the transmission power for PT-RS without reduction. Morespecifically, in Operation Example 3, transmitter 100 does not maintainthe power ratio ρ_(PTRS,i) between the data and PT-RS before adjustment.

As a result, the transmission power for PT-RS is not reduced in thePT-RS port, so that it is made possible to prevent degradation of thereception accuracy of PT-RS in receiver 200.

<Operation Example 4>

FIG. 12 illustrates an example of transmission power adjustment inOperation Example 4.

As illustrated in FIG. 12, transmitter 100 reduces the transmissionpower by transmitting nothing on some RE of the RE to which the data ismapped in the PT-RS port (antenna port 1000). That is, in OperationExample 4, transmitter 100 reduces the transmission power on some RE towhich the data signal has been mapped, and maintains the transmissionpower for the PT-RS and the data signal mapped to another part of the REwithout reduction.

As a result, since the transmission power for PT-RS and data in the REto be actually transmitted from transmitter 100 is not reduced in thePT-RS port, it is made possible to prevent degradation of the receptionaccuracy of PT-RS and data in receiver 200.

<Operation Example 5>

FIG. 13 illustrates an example of transmission power adjustment inOperation Example 5.

As illustrated in FIG. 13, transmitter 100 reduces the transmissionpower for PT-RS to the transmission power for the data signal in thePT-RS port (antenna port 1000). That is, transmitter 100 reduces thetransmission power for PT-RS and does not reduce the transmission powerfor the data signal in the PT-RS port.

In other words, as illustrated in FIG. 13, transmitter 100 sets thepower ratio ρ_(PTRS,i)=1 between the data and PT-RS, and transmits thePT-RS with the same “power per antenna port, per RE” as the data. Inother words, transmitter 100 releases power boosting of PT-RS.

Thus, the transmission power for the data signal is not reduced, so thatit is made possible to prevent degradation of the reception accuracy ofdata in receiver 200.

Note that, in FIG. 13, the case has been described in which thetransmission power for PT-RS is reduced to the transmission power forthe data signal, but without limitation to this case, transmitter 100may reduce the transmission power for PT-RS such that the transmissionpower for PT-RS does not to exceed the maximum transmission power of thePT-RS port. That is, the transmission power for PT-RS after adjustmentmay be larger or smaller than the transmission power for the datasignal.

Operation Examples 1 to 5 have been described, thus far.

As described above, in this embodiment, transmitter 100 transmits a datasignal with a defined transmission power while subjecting PT-RS to powerboosting and transmitting the PT-RS, when performing non-coherenttransmission or partial coherent transmission. At this time, in a casewhere the remaining power for transmission with the configuredtransmission power is not sufficient, transmitter 100 adjusts thetransmission power within a range not exceeding the maximum transmissionpower for each antenna port.

That is, transmitter 100 configures the transmission power for PT-RS anda signal (such as data) to be transmitted simultaneously with the PT-RSwithin a range not exceeding the maximum transmission power for eachantenna port. This configuration of transmission power may includeapplication and release of power boosting of PT-RS. Further, in a casewhere the transmission power configured in a PT-RS port exceeds themaximum transmission power for the PT-RS port, transmitter 100 adjuststhe transmission power to be less than or equal to the maximumtransmission power for each antenna port.

Thus, transmitter 100 is capable of transmitting PT-RS with the highestpossible transmission power within a range not exceeding the maximumtransmission power for each antenna port, in accordance with theremaining power of transmitter 100 even in a transmission for whichpower cannot be adjusted between antenna ports as in non-coherenttransmission or partial coherent transmission. Thus, the noiseestimation accuracy can be improved in receiver 200, and the improvementof the transmission speed/transmission efficiency can be expected.

Further, transmitter 100 adjusts the transmission power such that thetransmission power falls within a range not exceeding the maximumtransmission power for each antenna port, thereby making it possible toprevent transmission with a power lower than the intended power orprevent a signal from being distorted in a case where the remainingamount of the transmission power of transmitter 100 is small.

Note that how the transmission power configuration method describedabove (e.g., Operation Examples 1 to 5) is performed may be dependent onimplementation of transmitter 100. For example, transmitter 100 mayapply any method of Operation Examples 1 to 5 described above and adjustthe transmission power, and/or may select any method of OperationExamples 1 to 5 described above and adjust the transmission power, inaccordance with the radio state or the conditions.

In addition, transmitter 100 may cancel the configuration of thetransmission power reduction in a case where the remaining power oftransmitter 100 increases, for example, after the transmission power isreduced as in Operation Examples 1 to 5 described above.

Further, in the present embodiment, the calculation method of the ratioρ_(PTRs,i) indicated in Equation 2 is not limited to the abovedescription, and another method may be used.

Embodiment 2

In the present embodiment, a description will be given of a case where atransmitter, (i.e., mobile station) subjects PT-RS to power boosting andtransmits the PT-RS in uplink. Further, in the present embodiment, thebase station (receiver) indicates, to the mobile station, whether or notadjustment of the transmission power described in Embodiment isrequired.

[Overview of Communication System]

The communication system according to the present embodiment includesmobile station 300 (transmitter) and base station 400 (receiver). PT-RSis transmitted from mobile station 300 to base station 400.

[Configuration of Mobile Station]

FIG. 14 is a block diagram illustrating a configuration of mobilestation 300 (transmitter) according to the present embodiment. In FIG.14, the same components as those of Embodiment 1 (FIG. 6) are denoted bythe same reference numerals, and their descriptions are omitted.Specifically, in addition to the configuration of transmitter 100illustrated in FIG. 6, mobile station 300 illustrated in FIG. 14 furtherincludes receiver 302, signal demultiplexer 303, data demodulator 304,and error correction decoder 305. Further, operations of antenna 301,controller 306 and error correction encoder 307 differ partly from theoperations of antenna 106, controller 101 and error correction encoder102 illustrated in FIG. 6.

Antenna 301 radiates the signal to be inputted from transmitter 105toward base station 400. Further, antenna 301 receives the signaltransmitted from base station 400 and outputs the received signal toreceiver 302.

Receiver 302 applies radio reception processing, such as frequencyconversion, to the received signal to be inputted from antenna 301, andoutputs the signal after the radio reception processing to signaldemultiplexer 303.

Signal demultiplexer 303 demultiplexes DCI and a data signal from thesignal to be inputted from receiver 302, and outputs the DCI tocontroller 306 and outputs the data signal to data demodulator 304.

Data demodulator 304 demodulates the data signal to be inputted fromsignal demultiplexer 303 and outputs the demodulation signal to errorcorrection decoder 305.

Error correction decoder 305 decodes the demodulation signal to beinputted from data demodulator 304, extracts an RRC signal from theresultant received data signal, and outputs the RRC signal to controller306.

Controller 306 calculates a Power Headroom (PH) indicating the remainingtransmission power of mobile station 300, generates a Power HeadroomReport (PHR) to be reported to base station 400, and outputs the PHR toerror correction encoder 307. In addition, controller 306 determines thetransmission power for a transmission signal, such as a data signal andPT-RS, based on the information contained in the DCI to be inputted fromsignal demultiplexer 303 and the information contained in the RRC signalto be inputted from error correction decoder 305. The DCI or RRC signalmay include, for example, information indicating whether or notadjustment of the transmission power is required (or informationindicating adjustment of the transmission power). Controller 306 outputsthe determined transmission power information to signal assigner 104.

Error correction encoder 307 applies error correction coding to thetransmission data signal to be inputted or the PHR to be inputted fromcontroller 306 and output the signal resulting from the error correctioncoding to modulator 103.

[Configuration of Base Station]

FIG. 15 is a block diagram illustrating a configuration of base station400 (receiver) according to the present embodiment. Note that, in FIG.15, the same components as those of Embodiment 1 (FIG. 7) are denoted bythe same reference numerals, and their descriptions are omitted.Specifically, base station 400 illustrated in FIG. 15 further includescontroller 402, error correction encoder 403, modulator 404, signalassigner 405, and transmitter 406 in addition to the configuration ofreceiver 200 illustrated in FIG. 7. Further, operations of antenna 407,channel estimator 408, and error correction decoder 401 differ partlyfrom the operations of antenna 201, channel estimator 204, and errorcorrection decoder 207 illustrated in FIG. 7.

Error correction decoder 401 decodes the demodulation signal to beinputted from data demodulator 206 and outputs the resultant receiveddata signal. Further, error correction decoder 401 extracts the PHR fromthe data signal and outputs the PHR to controller 402.

Controller 402 determines whether or not mobile station 300 is to applythe transmission power control (transmission power adjustment) describedin Embodiment 1 based on the PHR to be inputted from error correctiondecoder 401. In addition, controller 402 determines, for example, asignal waveform, modulation coding scheme (MCS), and allocation band tobe applied to data transmission in mobile station 300. Controller 402generates, based on the determination result and determined content, aDCI (i.e., dynamic signaling) and RRC signal (i.e., higher layersignaling), and outputs the DCI to signal assigner 405 and outputs theRRC signal to error correction encoder 403.

Further, controller 402 outputs, to channel estimator 408, “informationon amplitude of PT-RS and/or the like” indicating whether or not thetransmission power control described in Embodiment 1 is applied to thesignal received from mobile station 300, based on the determinationresult regarding whether or not the transmission power adjustment isrequired. The information on amplitude of PT-RS and/or the like mayinclude, for example, information on the amplitude (power) ratio ofPT-RS and the data signal after the transmission power adjustment.

Error correction encoder 403 applies error correction coding to the RRCsignal to be inputted from controller 402 and outputs the signalresulting from the error correction coding to modulator 404.

Modulator 404 performs modulation processing on the signal to beinputted from error correction encoder 403 and outputs the signal afterthe modulation processing to signal assigner 405.

Signal assigner 405 maps the signal to be inputted from modulator 404and the DCI to be inputted from controller 402 to the time and frequencydomain and outputs the signal after the mapping to transmitter 406.

Transmitter 406 applies radio transmission processing, such as frequencyconversion using a carrier wave to the signal to be inputted from signalassigner 405, and outputs the signal after the radio transmissionprocessing to antenna 407.

Antenna 407 receives the signal transmitted from mobile station 300 (seeFIG. 14) and outputs the received signal to receiver 202. Antenna 407radiates (transmits) the signal to be inputted from transmitter 406toward mobile station 300.

Channel estimator 408 performs channel estimation, using DMRS to beinputted from signal demultiplexer 203. At this time, channel estimator408 may perform channel estimation, using PT-RS. When PT-RS is used,channel estimator 408 may determine the amplitude (power) ratio betweenPT-RS and the data signal based on the information on amplitude of PT-RSand/or the like to be inputted from controller 402. Channel estimator408 outputs the channel estimate (channel information) to datademodulator 206. Note that, in a case where no PT-RS is used in channelestimation performed by channel estimator 408, the information onamplitude of PT-RS and/or the like need not be inputted to channelestimator 408.

[Operations of Mobile Station 300 and Base Station 400]

Next, operations of mobile station 300 and base station 400 will bedescribed in detail.

Mobile station 300 performs a non-coherent transmission or partialcoherent transmission, using a high frequency band and a high modulationorder in uplink.

Base station 400 determines whether or not “the remaining power fortransmission with the configured transmission power in a PT-RS port isinsufficient,” that is, whether or not the transmission power adjustmentis required in mobile station 300.

Then, base station 400 indicates to mobile station 300 to apply thetransmission power adjustment described in Embodiment 1 in a case wherethe remaining power for transmitting the signal with the configuredtransmission power is not sufficient in the PT-RS port. That is, in acase where an indication for transmission power adjustment from basestation 400 is present, mobile station 300 adjusts the transmissionpower such that the transmission power is less than or equal to themaximum transmission power for each antenna port, as described inEmbodiment 1.

Hereinafter, specific Operation Examples 1 and 2 of mobile station 300and base station 400 will be described.

<Operation Example 1>

In Operation Example 1, mobile station 300 first calculates thetransmission power for the data signal, using a parameter and/or thelike indicated from base station 400. In addition, mobile station 300determines the transmission power for every RE in a PT-RS port, usingthe ratio ρ_(PTRS,i) indicated in Equation 2. That is, mobile station300 applies power boosting to PT-RS.

Next, mobile station 300 calculates a PH. The PH is, for example, avalue resulting from subtracting the transmission power for the datasignal in all the antenna ports calculated above from the maximumtransmission power of the entirety of mobile station 300. Then, mobilestation 300 reports the calculated PH to base station 400 as a PHR.

When the value of the received PHR is less than a threshold value, basestation 400 determines that there is no sufficient remaining power inthe PT-RS port in mobile station 300 and indicates adjustment(reduction) of transmission power to mobile station 300 as described inEmbodiment 1. This indication may be given explicitly or implicitly byan RRC signal or a DCI.

In a case where an indication for transmission power adjustment ispresent, as described in Embodiment 1, mobile station 300 reduces thetransmission power for PT-RS or a data signal and transmits the PT-RSand data signal and/or the like after the adjustment to base station400.

Thus, in Operation Example 1, in a case where the PHR to be calculatedusing the maximum transmission power of the entirety of mobile station300 and the transmission power for the data signal is less than athreshold value, base station 400 indicates adjustment of thetransmission power to mobile station 300. This allows a PHR similar toLTE to be used in the transmission power control, so that theconfiguration to be additionally implemented in mobile station 300 andbase station 400 for transmission power control can be reduced.

Note that, the description has been given of the case where the PHRrepresents the remaining power in all the antenna ports of mobilestation 300, but there is no limitation to this case. For example, thePHR may be a value resulting from subtracting the transmission power forthe data signal in a PT-RS port from the maximum transmission power inthe PT-RS port. That is, in a case where the PHR to be calculated usingthe maximum transmission power in the PT-RS port of mobile station 300and the transmission power for the data signal is less than thethreshold, adjustment of the transmission power is indicated from basestation 400 to mobile station 300, transmitter. As a result, basestation 400 is allowed to know the transmission power state of the PT-RSport in a more detailed manner, so that base station 400 can moreaccurately determine whether or not the transmission power needs to bereduced, and can appropriately provide an indication to mobile station300.

<Operation Example 2>

In Operation Example 2, as in Operation Example 1, mobile station 300first calculates the transmission power for the data, using a parameterand/or the like indicated from base station 400. In addition, mobilestation 300 determines the transmission power for every RE in a PT-RSport, using the ratio ρ_(PTRS,i) indicated in Equation 2. That is,mobile station 300 applies power boosting to PT-RS.

Meanwhile, base station 400 indicates, to mobile station 300, at leastone of a waveform (e.g., CP-OFDM or DFT-S-OFDM), MCS, and band (e.g.,the number of PRBs) used for transmission of the data signal.

Mobile station 300 determines whether or not to perform the transmissionpower adjustment as described in Embodiment 1, based on at least one ofthe waveform, MCS, and the band indicated from base station 400.

For example, in a case where the indicated waveform is “DFT-S-OFDM,” asdescribed in Embodiment 1, mobile station 300 reduces the transmissionpower for PT-RS or a data signal and transmits the PT-RS and data signaland/or the like after the adjustment to base station 400. This isbecause, in a case where the indicated waveform is DFT-S-OFDM (i.e.,single carrier waveform), the transmission power is likely to beextremely large because mobile station 300 is likely to be positioned ona cell edge.

Further, when the indicated MCS is “MCS of a level lower than thethreshold value,” mobile station 300 reduces the transmission power forPT-RS and the data signal and transmits the PT-RS and data signal afteradjustment to base station 400 as described in Embodiment 1. This isbecause, in a case where the indicated MCS is an MCS of a lower levelthan the MCS within a range of an MCS of a higher level with which PT-RSis transmitted, mobile station 300 is likely to be forced to performtransmission to base station 400 in a noisy environment, and thus, thetransmission power is likely to be high.

Further, when the indicated band is “broader than the threshold value,”mobile station 300 reduces the transmission power for PT-RS and the datasignal and transmits the PT-RS and data signal after adjustment to basestation 400 as described in Embodiment 1. This is because thetransmission power for data increases depending on the allocated band,and therefore, when the indicated band is broader than a certain value,there is a high possibility that the transmission power is large.

In this manner, mobile station 300 may determine whether or not toperform transmission power adjustment based on any one of a waveform,MCS and band used for data transmission or a plurality of parameters.

That is, base station 400 implicitly indicates, to mobile station 300,the presence or absence of application of transmission power control asdescribed in Embodiment 1, by the indication of at least one of awaveform, MCS, and band. This implicit indication does not require theuse of PHRs as described in Operation Example 1 in the transmissionpower control. For this reason, the configuration to be additionallyimplemented in mobile station 300 and base station 400 for transmissionpower control can be reduced.

Operation Examples 1 and 2 have been described, thus far.

As described above, in the present embodiment, mobile station 300transmits a data signal with a defined transmission power and subjectsPT-RS to power boosting, and transmits the PT-RS in non-coherenttransmission or partial coherent transmission. In a case where basestation 400 determines that the remaining power for transmission withthe configured transmission power is not sufficient in the PT-RS port ofmobile station 300, base station 400 indicates, to mobile station 300,adjustment for the transmission power within a range not exceeding themaximum transmission power for each antenna port. Mobile station 300performs a transmission power control in accordance with the instructionof base station 400.

Thus, mobile station 300 is capable of transmitting PT-RS with thehighest possible transmission power within a range not exceeding themaximum transmission power for each antenna port, in accordance with theremaining power of mobile station 300 even in a transmission for whichpower cannot be adjusted between antenna ports as in non-coherenttransmission or partial coherent transmission as in Embodiment 1. Thus,improvement in the transmission speed/transmission efficiency byimproving the noise estimation accuracy can be expected in base station400.

Further, mobile station 300 adjusts the transmission power such that thetransmission power falls within a range not exceeding the maximumtransmission power for each antenna port, thereby making it possible toprevent transmission with a power lower than the intended power and/orprevent a signal from being distorted in a case where the remainingamount of the transmission power of mobile station 300 is small.

Further, in the present embodiment, since base station 400 indicatestransmission power adjustment to mobile station 300, mobile station 300and base station 400 can communicate with each other in a state whererecognition of the transmission power between mobile station 300 andbase station 400 is the same.

Embodiment 3

In the present embodiment, a description will be given of a case where atransmitter (i.e., mobile station) subjects PT-RS to power boosting andtransmits the PT-RS in uplink. Further, in the present embodiment, themobile station determines whether or not adjustment of the transmissionpower is required as described in Embodiment 1.

[Overview of Communication System]

The communication system according to the present embodiment includesmobile station 500 (transmitter) and base station 600 (receiver). PT-RSis transmitted from mobile station 500 to base station 600.

[Configuration of Mobile Station]

FIG. 16 is a block diagram illustrating a configuration of mobilestation 500 (transmitter) according to the present embodiment. In FIG.16, the same components as those of Embodiment 1 (FIG. 6) are denoted bythe same reference numerals, and their descriptions are omitted.Specifically, operations of controller 501 and error correction encoder502 differ partly from the operations of controller 101 and errorcorrection encoder 102 illustrated in FIG. 6.

Controller 501 calculates the PH indicating the remaining transmissionpower of mobile station 500, generates a PHR to be reported to basestation 600, and outputs the PHR to error correction encoder 502.Further, controller 501 determines whether or not the transmission powercontrol (transmission power adjustment) described in Embodiment 1 is tobe applied, based on the calculated value of the PH. Then, controller501 determines the transmission power for a transmission signal, such asa data signal and PT-RS, in accordance with the result of determination.Controller 501 outputs the determined transmission power information tosignal assigner 104.

Error correction encoder 502 applies error correction coding to thetransmission data signal to be inputted or the PHR to be inputted fromcontroller 501 and output the signal resulting from the error correctioncoding to modulator 103.

[Configuration of Base Station]

FIG. 17 is a block diagram illustrating a configuration of base station600 (receiver) according to the present embodiment. In FIG. 17, the samecomponents as those of Embodiment 1 (FIG. 7) are denoted by the samereference numerals, and their descriptions are omitted. Specifically,base station 600 illustrated in FIG. 17 further includes controller 602in addition to the configuration of receiver 200 illustrated in FIG. 7.Further, operations of channel estimator 603 and error correctiondecoder 601 are different from the operations of channel estimator 204and error correction decoder 207 illustrate in FIG. 7.

Error correction decoder 601 decodes the demodulation signal to beinputted from data demodulator 206 and outputs the resultant receiveddata signal. Error correction decoder 601 extracts the PHR from the datasignal and outputs the PHR to controller 602.

Controller 602 determines whether or not mobile station 500 applies thetransmission power control described in Embodiment 1, based on the PHRsinputted from error correction decoder 601. Further, controller 602outputs, to channel estimator 603, “information on amplitude of PT-RSand/or the like” indicating whether or not the transmission powercontrol described in Embodiment 1 is applied to the signal received frommobile station 500, based on the result of determination.

Channel estimator 603 performs channel estimation, using DMRS to beinputted from signal demultiplexer 203. At this time, channel estimator603 may perform channel estimation, using PT-RS. When PT-RS is used,channel estimator 603 may determine the amplitude (power) ratio betweenPT-RS and the data signal based on the information on amplitude of PT-RSand/or the like to be inputted from controller 602. Channel estimator603 outputs the channel estimate (channel information) to datademodulator 206.

Note that, in a case where no PT-RS is used in channel estimation bychannel estimator 603, the configuration of base station 600 may beomitted, and the base station may have the same configuration asreceiver 200 illustrated in FIG. 7.

[Operations of Mobile Station 500 and Base Station 600]

Next, operations of mobile station 500 and base station 600 will bedescribed in detail.

Mobile station 500 performs non-coherent transmission or partialcoherent transmission, using a high frequency band and a high modulationorder in uplink.

Further, mobile station 500 determines whether or not “the remainingpower for transmission with the configured transmission power in a PT-RSport is insufficient,” that is, whether or not the transmission poweradjustment is required.

Then, mobile station 500 performs the transmission power adjustmentdescribed in Embodiment 1 in a case where the remaining transmissionpower for transmitting the signal with the configured transmission poweris not sufficient in the PT-RS port.

Meanwhile, base station 600 determines whether or not “the remainingpower for transmission with the configured transmission power in a PT-RSport is insufficient” as with mobile station 500. Then, in a case wherethe remaining power for transmitting a signal with the configuredtransmission power is not sufficient in the PT-RS port, base station 600determines that the signal is transmitted in mobile station 500 afterapplication of the transmission power control described in Embodiment 1.In this case, base station 600 performs channel estimation inconsidering, for example, that the transmission power for PT-RS or thedata signal is reduced.

Hereinafter, a specific operation example of mobile station 500 and basestation 600 will be described.

In the operation example, mobile station 500 first calculates thetransmission power for the data signal, using a parameter and/or thelike indicated from base station 600. In addition, mobile station 500determines the transmission power for every RE in the PT-RS port, usingthe ratio ρ_(PTRS,i) indicated in Equation 2. That is, mobile station500 applies power boosting to PT-RS.

Next, mobile station 500 calculates a PH.

The PH is, for example, a value resulting from subtracting thetransmission power for the data signal in all the antenna portscalculated above from the maximum transmission power of the entirety ofmobile station 500. Then, mobile station 500 reports the calculated PHto base station 600 as a PHR.

Further, when the calculated value of PH is less than a threshold value,mobile station 500 determines that the remaining power is not sufficientin the PT-RS port of mobile station 500, reduces the transmission powerfor PT-RS or the data signal, as described in Embodiment 1, andtransmits the PT-RS and data signal and/or the like after the adjustmentto base station 600.

Likewise, in a case where the value of PHR to be reported from mobilestation 500 is less than a threshold value, base station 600 determinesthat the transmission power adjustment as described in Embodiment 1 hasbeen applied to the received data signal or PT-RS, and performs channelestimation taking the reduction of transmission power intoconsideration.

Thus, in the operation example, in a case where the PHR to be calculatedusing the maximum transmission power of the entirety of mobile station500 and the transmission power for the data signal is less than athreshold value, mobile station 500 adjusts the transmission power, andbase station 600 determines that adjustment for transmission power isperformed in mobile station 500. This allows a PHR similar to LTE to beused in the transmission power control, so that the configuration to beadditionally implemented in mobile station 500 and base station 600 fortransmission power control can be reduced.

Note that, the description has been given of the case where the PHRrepresents the remaining power in all the antenna ports of mobilestation 500, but there is no limitation to this case. For example, thePHR may be a value resulting from subtracting the transmission power forthe data signal in a PT-RS port from the transmission power for a datasignal in the PT-RS port. That is, in a case where the PHR calculatedusing the maximum transmission power in the PT-RS port of mobile station500 and the transmission power for the data signal is less than thethreshold value, mobile station 500 adjusts the transmission power. As aresult, mobile station 500 and base station 600 are allowed to know thetransmission power state of the PT-RS port in a more detailed manner, sothat mobile station 500 and base station 600 can more accuratelydetermine whether or not the transmission power needs to be reduced.

The operation example has been described, thus far.

As described above, in the present embodiment, mobile station 500transmits a data signal with a defined transmission power, subjectsPT-RS to power boosting and transmits the PT-RS in non-coherenttransmission or partial coherent transmission. In this case, in a casewhere mobile station 500 determines that the remaining power fortransmission with the configured transmission power is not sufficient inthe PT-RS port of mobile station 500, mobile station 500 adjusts thetransmission power within a range not exceeding the maximum transmissionpower for each antenna port.

This allows mobile station 500 to transmit PT-RS with the highestpossible transmission power within a range not exceeding the maximumtransmission power for each antenna port, in accordance with theremaining power of mobile station 500 even in a transmission for whichpower cannot be adjusted between antenna ports as in non-coherenttransmission or partial coherent transmission as in Embodiment 1. Thus,improvement in the transmission speed/transmission efficiency byimproving the noise estimation accuracy in base station 600 can beexpected.

Further, mobile station 500 adjusts the transmission power such that thetransmission power falls within a range not exceeding the maximumtransmission power for each antenna port, thereby making it possible toprevent transmission with a power lower than the intended power orprevent a signal from being distorted in a case where the remainingamount of the transmission power of mobile station 500 is small.

Further, in the present embodiment, mobile station 500 determineswhether or not to adjust transmission power, thereby enablingconfiguration of an appropriate transmission power without waiting foran indication of base station 600.

Each embodiment of the present disclosure has been described, thus far.

(Other Embodiments)

(1) The term “CPE/ICI correction” used in the above embodiments means“correcting CPE,” “correcting ICI,” or “correcting both CPE and ICI.”

(2) Although the above embodiments mainly assume uplink transmission,the transmission power control described above may also be applied todownlink transmission.

(3) In the above embodiments, non-coherent transmission and partialcoherent transmission are assumed, but the content of the presentdisclosure can be applied to methods other than these transmissions.

(4) In the above embodiments, the description has been given of the caseof transmitting data, using two antenna ports (1000, 1001), as anexample. However, the number of antenna ports for transmitting data isnot limited to two, and the number of antenna ports other than two maybe used. However, it is assumed that power boosting of PT-RS is notapplied when the number of antenna ports from which data can betransmitted is one, because “use of the power of resources not used byanother antenna port” is impossible.

Further, although the description has been given of the case where PT-RSis mapped for one antenna port, the number of antenna ports for whichPT-RS is mapped is not limited to one. The number of antenna ports forwhich PT-RS is mapped may be two or more.

(5) The PHR used in Embodiments 2 and 3 may be transmitted periodicallyin time or may be transmitted each time the remaining transmission powerchanges. In addition, application and release of the reduction oftransmission power described in Embodiment 1 may be switched each timethe remaining transmission power surplus changes.

(6) When control channels (Physical Downlink Control Channel (PDCCH))and Physical Uplink Control Channel(PUCCH)), and data channels (PhysicalDownlink Shared Channel (PDSCH)) and (Physical Uplink Shared Channel(PUSCH)) are frequency-multiplexed, PT-RS may be mapped to this symbol.

(7) In the above embodiments (FIG. 1), the length of slot is assumed tobe 14 symbols, but the length of slot is not limited to 14 symbols, andfor example, the length of slot may be 7 symbols or another number ofsymbols.

(8) The present disclosure can be realized by software, hardware, orsoftware in cooperation with hardware. Each functional block used in thedescription of each embodiment described above can be partly or entirelyrealized by an LSI such as an integrated circuit, and each processdescribed in each embodiment may be controlled partly or entirely by thesame LSI or a combination of LSIs. The LSI may be individually formed aschips, or one chip may be formed so as to include a part or all of thefunctional blocks. The LSI may include a data input and output coupledthereto. The LSI herein may be referred to as an IC, a system LSI, asuper LSI, or an ultra LSI depending on a difference in the degree ofintegration. However, the technique of implementing an integratedcircuit is not limited to the LSI and may be realized by using adedicated circuit, a general-purpose processor, or a special-purposeprocessor. In addition, a Field Programmable Gate Array (FPGA) that canbe programmed after the manufacture of the LSI or a reconfigurableprocessor in which the connections and the settings of circuit cellsdisposed inside the LSI can be reconfigured may be used. The presentdisclosure can be realized as digital processing or analogue processing.If future integrated circuit technology replaces LSIs as a result of theadvancement of semiconductor technology or other derivative technology,the functional blocks could be integrated using the future integratedcircuit technology. Biotechnology can also be applied.

(9) The present disclosure can be implemented in apparatuses, devices,and systems of any kind, each being provided with a communicationfunction, (collectively referred to as “communication apparatuses”).Non-limiting examples of the communication apparatuses includetelephones (such as portable phones and smartphones), tablets, personalcomputers (PCs) (such as laptops, desktops, and notebooks), cameras(such as digital still/video cameras), digital players (such as digitalaudio/video players), wearable devices (such as wearable cameras,smartwatches, and tracking devices), game consoles, digital bookreaders, telehealth telemedicine (remote healthcare medicineprescription) devices, communication-function-equipped vehicles ortransportation (such as automobiles, airplanes and ships), and acombination of the above mentioned apparatuses of various kinds.

The communication apparatuses are not limited to portable or mobileapparatuses and thus include unportable or fixed apparatuses, devices,and systems of any kind, such as smart home devices (e.g., appliances,lighting equipment, smart meters or measuring instruments, and controlpanels), vending machines, and Internet of Things (“IoT” (every “things”that may exist on networks.

(10) In addition to data communication via cellular systems, wirelessLAN systems, communication satellite systems and/or the like,communication includes data communication via a combination of thesesystems.

(11) Moreover, the communication apparatuses include devices, such ascontrollers or sensors to be connected to or linked to a communicationdevice which executes communication functions described in the presentdisclosure. Controllers or sensors are included, for example, each ofwhich is configured to generate a control signal and/or a data signalused by the communication device which executes the communicationfunctions of the communication apparatuses.

(12) Further, the communication apparatuses include infrastructureequipment which performs communication with the above-mentionednon-limiting apparatuses of various kinds or which controls thesenon-limiting apparatuses of various kinds, such as base stations, accesspoints, apparatuses of any other kinds, devices, and systems.

A transmitter according to the present disclosure includes: controlcircuitry, which, in operation, determines a transmission power for aphase tracking reference signal (PT-RS) and a data signal within a rangenot exceeding a maximum transmission power for each antenna port; andtransmission circuitry, which, in operation, transmits the PT-RS and thedata signal with the determined transmission power.

In the transmitter according to the present disclosure, the controlcircuitry adjusts the transmission power to be less than or equal to themaximum transmission power for each antenna port in a case where thetransmission power configured in a first antenna port from which thePT-RS is transmitted exceeds the maximum transmission power of the firstantenna port.

In the transmitter according to the present disclosure, the controlcircuitry reduces the transmission power for the PT-RS and the datasignal transmitted from all antenna ports while maintaining a powerratio between the PT-RS and the data signal.

In the transmitter according to the present disclosure, the controlcircuitry reduces the transmission power in the first antenna port anddoes not reduce the transmission power in another antenna port exceptfor the first antenna port.

In the transmitter according to the present disclosure, the controlcircuitry reduces the transmission power for the PT-RS and the datasignal transmitted from the first antenna port while maintaining thepower ratio between the PT-RS and the data signal.

In the transmitter according to the present disclosure, the controlcircuitry reduces the transmission power for the data signal and doesnot reduce the transmission power for the PT-RS in the first antennaport.

In the transmitter according to the present disclosure, the controlcircuitry reduces the transmission power for part of resource elementsto which the data signal is mapped and does not reduce the transmissionpower for the data signal and the PT-RS which are mapped to otherresource elements, except for the part of the resource elements in thefirst antenna port.

In the transmitter according to the present disclosure, the controlcircuitry reduces the transmission power for the PT-RS and does notreduce the transmission power for the data signal in the first antennaport.

In the transmitter according to the present disclosure, the transmitteris a mobile station, and the control circuitry adjusts the transmissionpower to be less than or equal to the maximum transmission power foreach antenna port in a case where an indication from a base station ispresent.

In the transmitter according to the present disclosure, adjustment ofthe transmission power is indicated from the base station to thetransmitter in a case where a Power Headroom Report (PHR) calculatedusing a maximum transmission power of an entirety of the transmitter andthe transmission power for the data signal is less than a thresholdvalue.

In the transmitter according to the present disclosure, adjustment ofthe transmission power is indicated from the base station to thetransmitter in a case where a Power Headroom Report (PHR) calculatedusing a maximum transmission power in an antenna port of the transmitterfrom which the PT-RS is transmitted and the transmission power for thedata signal is less than a threshold value.

In the transmitter according to the present disclosure, the controlcircuitry determines whether or not to perform adjustment of thetransmission power, based on at least one of a signal waveform, amodulation coding scheme, and an allocated band indicated by the basestation.

In the transmitter according to the present disclosure, the transmitteris a mobile station, and the control circuitry adjusts the transmissionpower to be less than or equal to the maximum transmission power foreach antenna port.

In the transmitter according to the present disclosure, the controlcircuitry adjusts the transmission power in a case where a PowerHeadroom Report (PHR) calculated using the maximum transmission power ofan entirety of the transmitter and the transmission power for the datasignal is less than a threshold value.

In the transmitter according to the present disclosure, the controlcircuitry adjusts the transmission power in a case where a PowerHeadroom Report (PHR) calculated using the maximum transmission power inan antenna port of the transmitter from which the PT-RS is transmittedand the transmission power for the data signal is less than a thresholdvalue.

A transmission method according to the present disclosure includes:determining a transmission power for a phase tracking reference signal(PT-RS) and a data signal within a range not exceeding a maximumtransmission power for each antenna port; and transmitting the PT-RS andthe data signal with the determined transmission power.

The disclosure of Japanese Patent Application No. 2018-025861, filed onFeb. 16, 2018, including the specification, drawings, and abstract isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

One exemplary embodiment of the present disclosure is useful in mobilecommunication systems.

REFERENCE SIGNS LIST

-   100, 300, 500 Transmitter-   101,306,402,501,602 Controller-   102, 307, 403, 502 Error correction encoder-   103, 404 Modulator-   104, 405 Signal assigner-   105, 406 Transmitter-   106, 201, 301, 407 Antenna-   200, 400, 600 Receiver-   202, 302 Receiver-   203, 303 Signal demultiplexer-   204, 408, 603 Channel estimator-   205 CPE/ICI estimator-   206, 304 Data demodulator-   207, 305, 401, 601 Error correction decoder

1.-16. (canceled)
 17. A transmission apparatus, comprising: circuitry,which, in operation, adjusts, based on an indication from a basestation, a transmission power of a phase tracking reference signal(PT-RS); and a transmitter, which, in operation, transmits the PT-RS atthe adjusted transmission power.
 18. The transmission apparatusaccording to claim 17, wherein the circuitry, in operation, adjusts thetransmission power of the PT-RS to be less than or equal to a maximumtransmission power of an antenna port from which the PT-RS istransmitted.
 19. The transmission apparatus according to claim 17,wherein the circuitry, in operation, adjusts the transmission power ofthe PT-RS based on a power ratio between the PT-RS and a data signal.20. The transmission apparatus according to claim 17, wherein thecircuitry, in operation, based on the indication, adjusts thetransmission power of an antenna port from which the PT-RS istransmitted and does not adjust a transmission power of another antennaport.
 21. The transmission apparatus according to claim 17, wherein thecircuitry, in operation, adjusts the transmission power of the PT-RSwhile maintaining a power ratio between the PT-RS and a data signal. 22.The transmission apparatus according to claim 17, wherein the circuitry,in operation, determines, based on the indication, whether or not thetransmission power of the PT-RS is adjusted.
 23. The transmissionapparatus according to claim 17, wherein the circuitry, in operation,adjusts the transmission power in a case where a Power Headroom Report(PHR), which is calculated using a maximum transmission power of thetransmitter and a transmission power of a data signal, is less than athreshold value.
 24. The transmission apparatus according to claim 17,wherein the circuitry, in operation, adjusts the transmission power in acase where a Power Headroom Report (PHR), which is calculated using amaximum transmission power of an antenna port from which the PT-RS istransmitted and a transmission power of a data signal, is less than athreshold value.
 25. The transmission apparatus according to claim 17,wherein the circuitry, in operation, determines, based on at least oneof a signal waveform, a modulation coding scheme, and an allocated bandindicated by the base station, whether or not to adjust the transmissionpower per resource element (RE) of the PT-RS to be larger than atransmission power per RE of a data signal.
 26. A transmission method,comprising: adjusting, based on an indication from a base station, atransmission power of a phase tracking reference signal (PT-RS); andtransmitting the PT-RS at the adjusted transmission power.
 27. Thetransmission method according to claim 26, wherein the adjustingincludes adjusting the transmission power of the PT-RS to be less thanor equal to a maximum transmission power of an antenna port from whichthe PT-RS is transmitted.
 28. The transmission method according to claim26, wherein the adjusting includes adjusting the transmission power ofthe PT-RS based on a power ratio between the PT-RS and a data signal.29. The transmission method according to claim 26, wherein the adjustingincludes, based on the indication, adjusting the transmission power ofan antenna port from which the PT-RS is transmitted and not adjusting atransmission power of another antenna port.
 30. The transmission methodaccording to claim 26, wherein the adjusting includes adjusting thetransmission power of the PT-RS while maintaining a power ratio betweenthe PT-RS and a data signal.
 31. The transmission method according toclaim 26, comprising determining, based on the indication, whether ornot the transmission power of the PT-RS is adjusted.
 32. Thetransmission method according to claim 26, wherein the adjustingincludes adjusting the transmission power in a case where a PowerHeadroom Report (PHR), which is calculated using a maximum transmissionpower of the transmitter and a transmission power of a data signal, isless than a threshold value.
 33. The transmission method according toclaim 26, wherein the adjusting includes adjusting the transmissionpower in a case where a Power Headroom Report (PHR), which is calculatedusing a maximum transmission power of an antenna port from which thePT-RS is transmitted and a transmission power of a data signal, is lessthan a threshold value.
 34. The transmission method according to claim26, comprising determining, based on at least one of a signal waveform,a modulation coding scheme, and an allocated band indicated by the basestation, whether or not to adjust the transmission power per resourceelement (RE) of the PT-RS to be larger than a transmission power per REof a data signal.